When photographing a subject, there has been widely used a camera which includes a photographic lens or so-called zoom lens having variable magnification function to change a magnification ratio of photograph, if necessary. The zoom lens is configured to change a magnification ratio between a telescopic state capable of photographing a faraway subject in an enlarged state and a wide angle state capable of photographing the subject in a wider field angle, by operating a manipulation switch provided in a camera.
The zoom lens is composed of a combination of a plurality of lens groups each of which is formed by one or more lenses. A magnification ratio of the zoom lens is changed by moving each of the plurality of lens groups along an optical axis.
Here, there is known a lens driving-control device including a mechanical device, for example, a cam mechanism to drive the plurality of lens groups simultaneously and a lens driving-control device to drive the cam mechanism by hand and motors (for reference, see Japanese Patent Application Publication No. 06-160699).
However, there is a problem that the lens driving-control device as disclosed in Japanese Patent Application Publication No. 06-160699 has a complicated structure because the mechanical driving mechanism is provided.
On the other hand, it is possible to accomplish a lens driving-control device having a simple structure, which includes a motor provided every each lens group and is configured to drive lens groups independently by corresponding motors.
However, because the plurality of lens groups constituting zoom lens groups are disposed on the same optical axis, and a part of movable range of one of the adjacent lens groups along the optical axis is overlapped with a part of movable range of other lens group, if the lens groups are simultaneously driven, there is possibility that the lens groups interfere depending on an arrangement of the lens groups along the optical axis or driving speed.
On the contrary, in a sequential driving system in which the plurality of lens groups are driven or stopped in sequence from a subject side or image side, there is no fear that the lens groups interfere, but a long time takes between a driving initiation and a driving completion, compared to a case where the plurality of lens groups are simultaneously driven.
Also, because a focus lens group to perform a focus function of an image on an image surface is usually included in the zoom lens, until the drive of the focus lens group is completed, the focused image is not projected on the image surface.
Consequently, when the lens driving-control device of the sequential driving system is applied to a still camera or video camera having a structure for displaying the image projected on a CCD, CMOS or the like on a liquid crystal monitor, there is a problem that it takes a long time at which the image which is not focused is displayed and the camera or the like has no-good usability and attractiveness.